In studies of obsessive-compulsive disorder (OCD) co-morbidity, 59 OCD patients were found to have a substantial overlap in eating disorder-related symptoms, with intermediate eating disorder inventory scores between patients with anorexia nervosa or bulimia nervosa and healthy controls. Patients with the focal dystonia, blepharospasm, were found to share significantly more OCD-related symptoms than healthy controls. In psychobiologic studies, OCD patients exhibited no differences in arterial plasma catecholamine concentrations compared to healthy controls when both groups were sampled over time in an anxietyinducing situation - a finding congruent with other data that continue to reveal more serotonin-related abnormalities than other neurotransmitter system differences in OCD patients. In one of the first studies of neuropeptides in this disorder, patients with OCD were found to have abnormalities in the regulation of vasopressin and corticotrophin releasing factor secretion.